We're making a short sci-fi film set on Mars, called Last Flight. It's about the last woman left alive - - and 20 minutes of air.

As space fans ourselves, we're determined to make this a great little Mars film - an accurate and realistic portrayal of the red planet, as well as just a good, solid story.

As part of the production process we've therefore opened up the script, storyboard and other parts of the film for feedback and criticism online, in the hope of getting as many interested people thinking about the movie as possible.

Anyone is welcome to comment and send in their thoughts - and we'd love to hear any bright ideas you have, of a scientific, creative or speculative nature.

I'll weigh in on this one. A few do's and dont's for you, here -- mostly dont's, I'm afraid. These are sort of general guidelines, not comments on your story, sorry to say.

- Don't just film it in the desert and then tint everything red. That's really hokey and looks terrible.

- Don't have lots of free pieces of fabric flapping in the breeze. Martian winds are normally rather benign, and as thin as the air is, it takes a really good gust to make something like a flag or a tent whip around noticeably. Very small threads and other very light things (like the wind telltale on Phoenix) move around a good deal, but, for example, instead of showing a flag rippling in the wind, you'd show a flag twitching a bit around the edges and threads hanging off the flag moving more quickly.

- Do try and at least suggest the .38 Earth gravity. Things fall more slowly than they do on Earth, but not as slowly as they do on the Moon. And try to avoid just having people move normally and suggest low gravity by slowing down the film. The juxtaposition of people moving at normal speed and things falling slowly is important in suggesting low gravity.

- Don't show big fluffy cumulous clouds in the sky. Martian clouds tend to resemble cirrus clouds more than anything else, though they're not nearly as far above the ground as cirrus clouds are here on Earth. Think light and feathery.

- Make the sky pinkish-orangish, and make the brightening of the sky near the horizon more pronounced than you would see on Earth. The sky doesn't get tremendously dark at zenith, but especially during spring and summer at low latitudes, there's a lot more dust entrained in the air in the first couple thousand feet above the ground than there is above that. Looking horizontally towards the horizon, you're looking through more dust, which backscatters the light and makes the sky near the horizon look brighter.

- The Sun looks pretty white up high in the sky, with a slightly reddish tinge. It looks more bluish, and the sky around the Sun looks bluish, at sunrise and sunset. It's the opposite of what you see on Earth, when the sky is reddish at sunrise and sunset and blue when the Sun is high in the sky.

- While this isn't ubiquitous, a lot of the soils on Mars have a somewhat hardened "armoring" layer on the very top surface. It's been called a duricrust, and while it's present in a lot of places, it's not seen on every single example of Martian soil. When it does occur, it's very thin, but it can push away from the underlying soil in somewhat choesive, through crumbley, sheets. Think of snow drifts after a day when it gets up to about 38 degrees Fahrenheit (or 3 or so degrees Celsius), where the very upper layer of snow has slightly melted and re-frozen as the day grew cooler.

- Don't forget that it's very cold on Mars. Even in those places where the daytime high temperatures reach up to 60 or 70 degrees F, it can get down well below zero F at night, even in the summer. And the warmest temperatures usually only occur in the first foot or two over the ground. The air thins out rapidly and it cools down rapidly as you disengage from the ground warming effect -- the air is so thin that mixing doesn't occur as efficiently as it does on Earth. In short, standing on Mars your feet can be comfortable while your head is quite chilly. And at night, no matter where you are, it's *really* cold.

- Martian dust devils are not tornados. They can pick up dust and maybe sand-sized grains, but most aren't powerful enough to pick up something the size of a pebble. They seem to clean dust *off* of pebbles, in fact. The blow away dust -- not houses. They generally pose very little physical threat to humans or their equipment. They look dramatic, but they're mostly harmless.

- Lots of places on Mars are very rocky, but some aren't nearly as rocky as others. The rockiest terrain we've ever landed on was at the Viking 2 landing site, followed by the Pathfinder site and then the Viking 1 site. It's still rocky at the Spirit site, though not as much so as at the previous three. And there are very, very few rocks littering the surface where Opportunity landed, or where Phoenix landed (though the polar terrain at the Phoenix site does have more surface rocks than Oppy's Meridiani site, which has the fewest surface rocks of anywhere we've seen from the surface). In actuality, a lot of Mars is covered with ancient sand dunes and dust ripples.

- There are a lot of craters on Mars, but not nearly as many per acre (or hectare) as on the Moon. Most of the Moon's surface is at crater saturation on most every scale -- every new crater obliterates an older one, so additional cratering doesn't much increase the total count. Mars isn't like that, and has relatively few small craters of less than 100 meters or so in diameter. That's because Mars' thin atmosphere burns up the smaller impactors, removing much of the small-to-tiny end of the cratering range.

- Liquid water can only exist on the surface of Mars in a very small number of locations, and even then only during the warmest parts of the day. Most of Mars' surface is below the "triple point" of pressure and temperature that allows water to exist. Ice doesn't melt most places on Mars, it mostly sublimates directly into vapor. The places where water could exist for brief periods while on the surface tend to be very low areas where the air pressure is highest, such as on the floor of the giant impact basin Hellas.

I imagine that's enough for now. Hopefully at least some of these items are useful to your endeavour... *grin*...

-the other Doug

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